Cathode ray tube oscillograph apparatus



Oct. 29, 1940. L.M.IMYERS ET AL CATHODE RAY TUBE OSCILLOGRAPH APPARATUS Filed Dec. 19, l935 [g5 if -5 23i:

'zg-Fq INVENTOR. LEONARD M. MYERS ROBERT CADZOW ATTORNEY.

Patented Oct. 29, 1940 UNITED STATES GATHODE RAY Tomi OSCILLQGRAPH- f APPARATUS Leonard Morris Myers, Middlesbrouglif-England, and Robert Cadzow, Ardentinny, Scotland, as-

signors to Radio Oorporationiof.

poration of Delaware This invention relates to cathode ray'tube oscillograph apparatus suitable for use for television and similar oscillograph apparatus.

The object of the invention is to provide improved oscillograph arrangements having simplified and reliable scanning means, i. e., means whereby the cathode ray beam may be caused to scan a predetermined picture area.

. It is common practice at the present time to obtain scanning action in a cathode ray tube oscillograph apparatus by means of angularly dis-,

posed cathode ray-deflecting devices to which suitable current or-voltage wave forms are ap- Ig. plied, said wave forms being derived from relaxaand discharging the same at predetermined intervals, the invention being characterised by the fact that the discharge of the condenser is obtained by completing a. circuitincluding at least a part of the cathode ray beam itself said circuit being completed when the said beam reaches one end of a scanning path.

. One form of cathode ray tube in accordance with this invention comprises at least one electrode (additional to the normally provided ray deflecting plates in. the case of a tube designed f orelectrostatic deflection) said electrode beingso positioned as to be struck by the cathode ray beam at the ends of its paths of traversal. In the usual arrangement wherein scanning'action is obtained by deflection of the beam in mutually perpendicular directions so that the beam is scanned in a series of substantially parallel and substantially straight lines the tube is provided .with two mutually perpendicular electrodes (additional to electrostatic deflector plates, if any which together either constitute two adjacent edges/of the picture area scanned or, more usu ally constitute two adjacent edges of a projection of said area. I j

The invention is illustrated in the accompanying drawing in which 'Fig. 1 shows one embodiment of my; invention. wherein an auxiliary electrode is positioned with- 'ericaga corirr'; a cathqtle ray tube tocooperate'withthe beam.

for'producing'deflecting potentials; f Fig. 2 shows a modification of the embodiment of my invention shown in Fig. l in which the auxiliary;electrodeiis dispensed with; .and' 7 :Fi gQQ ShOWS afurther'embodiment of my invention and jaf'modification of thatshown'jin' "Referring to Figure 1, the tube therein 'sche; V rjnatically-Trepresented comprises theus'ual elecl0 tron gun andj'two mutually perpendicular of electrostaticdeflecting plates; Associated with eachi'pa ,o 'ge e tins lat is. an addi i nal strip like electrode, said strip-like electrodesfbe' ing mutually perpendicular and being positioned along two of the adjacent edges of the areato be scanned by the beam. For the sake of convenience in description and drawing only one pair I of electrostatic plates and one additional N strip-like electrode 2 are illustrated in Figure 1 2'0 and described below (this simplified method of representation is adopted for all the figures), but it is to beunderstood that there are two pairs. of plates and two additional strip-like electrodes r in perpendicular relationship, the operation being similar for both of the two perpendicular arrangements.

The strip-like electrode 2 is connected to one of the electrostatic deflecting plates of the pair I which co-operate therewith and said one plate is connected through a condenser 3 to the positive terminal of a source 4 of potential whose negative terminal is connected to the cathode 5.

Said one plate is also connectedthrough a resist; Z

ance 6 to the positive terminal of 'a" iseoond f source I of potential whose negative terminal is connected to the anode 8 of the electron gun and also to the positive terminal of the sourced.

The source I is shunted by a potentiomete'r rean sistance' 9 an adjustable tapping point-Ill, upon 40" which is connected to the other of the pair I of electrostatic deflecting plates. The filament 5 of the electron gun is heated in the usual-way The condenser 3 which is connected betweenthe anode 8 and the strip-like electrode 2 is continuously chargedthrough the resistanceiso '55 that for a period of time which will depend upon the constants of the circuit, that terminal of the condenser 3 which is directly connected to one of the deflector plates I will become more and more positive and the electron beam in the tube will be consequently deflected further and further until it finally impacts upon the strip-like electrode 2. Thereupon the condenser will be discharged at a high speed and the beam will return to its original position. The speed at which the operating action takes place is controlled largely by the value of the resistance 6. This resistance though shown inFigure 1 in the ordinary conventional manner is preferably constituted by some constant current devicesuch as a diode so as to ensure rectilinear operation. The adjustable tapping point I0 upon the potentiometer resistance 9 serves for centering purposes.

The single pair I of deflector plates and cooperating condenser 3 resistance 6 and striplike electrode Ziprovide one component of scanning. The other component of scanning may be provided in a similar manner.

In a modification (not illustrated) the incidence of the cathode ray on the strip-alike electrode is not utilised directly to discharge the condenser 6 but instead impulses caused by that incidence are applied to the grid of a thermionic valve-for example, a triode-whose anode-cathode space is shunted across the condenser, the arrangement being such that when said impulses are applied to said grid the internal resistance of the valve becomes of low value and thus the condenser is discharged.

In another way of carrying out this invention there is provided in association with a cathode ray tube a condenser which is continuously charged at a predetermined rate and one terminalof which provides potential for deflecting the cathode ray beam. The arrangement is such that when the cathode ray beam has been defiected apredetermined amountthat is to say the potential of said condenser terminal has risen to a predetermined value-the cathode ray beam itself completes a circuit for discharging the condenser (preferably directly through the said beam) whereupon the said beam returns to its original position and is again deflected as the potential of the said condenser terminal rises again due to the continuous charging of the said condenser.

In the construction shown in Figure 2 and which operates generally as set 'forth in the last paragraph, there is provided Within a cathode ray tube a pair of condenser electrodes l4, l5, one (l4) of which is connected through a charging resistance l6 of say 1 to 2 megohms to a suitable source il' of potential-for example a 1,000 volt sourcehaving its negative terminal connected to the cathode I8 of the electron gun. The charging resistance I6 may be a. constant current device, such as a diode, in order to ensure rectilinearity of charge or, if this is not'convenient, the values of the circuit may be so selected that the charging only takes place over the substantially straight portion of the normal exponential charging curve of the condenser. The other electrode l of the condenser is connected to a suitable tapping point l9 upon the source I1 and also to the anode of the electron gun whose cathode is shown at l8. The electrodes l4, 15, are .so positioned in the tube that the length of "the cathode ray beam between the cathode and the said condenser is such as to give a desired electron jet resistance, e. g., one somewhere about 1 megohm. This jet resistance is represented in broken lines at 20 in Figure 2. The electrode l4 may be connected to one of a pair of deflector plates 43 the other plate being connected to a point of fixed potential, for example the anode of the electron gun. It will be seen that with this arrangement as the potential of the condenser electrode I4 rises due to the accumulation of charge in the said condenser, the cathode ray beam will be deflected further and further, and the arrangement is such that when the required deflection has been obtained the said cathode ray beam strikes the said condenser electrode M (which may have one edge bent over as shown at Mo to receive the beam, if desired) the condenser being accordingly discharged through the electron beam to the electron gun. If desired, and preferably the condenser is constituted by the capacity existing between a pair of electrostatic deflector plates provided for deflecting the beam, 1. e., the electrodes |4, l5, also constitute the deflector plates. As will be obvious Figure 2 is purely schematicfor example there is shown only a simple 'filament l3 though, of course, in practice an electron gun with a control electrode would be provided.

The speed of scan and the ratio of scan time for fly back time will depend upon the value of the condenser 4| 5, the value of the charging resistance It and the other constants of the circuit. If desired the condenser may be shuntted by an adjustable condenser 45 provided outside the tube. It will be appreciated that the arrangement just described will provide for one component of scanning and of course the second normally perpendicular component of scanning may be obtained in a similar way.

In the modification shown in Figure 3 the cathode of the tube is represented at 2|, the control electrode (Wehnelt cylinder) at 22, the electron .gun anode at 23, and one pair of deflector plates at 24. A conductor strip 25 is provided just beyond one of the plates 24 and is connected through a condenser 26 shunted by a suitable short circuiting arrangement 2'|-e. g., a glow discharge tubeto the grid 28 of a triode 29said grid being also connected to the cathode 36 of the triode through a resistance 3|. The circuit is completed from cathode 30 to gun anode 23 through a battery 32 whose positive terminal is towards the anode. Signals set up across the output resistance 33 of the valve 29 are applied via terminals 34 to control a time base circuit 47. With this arrangement when the cathode ray strikes the strip 25 a circuit is completed through the ray and via elements 25, 21, 3|, "32 to 23. When this circuit 'is completed a small proportion of the electron current will pass through resistance 3|, this being made possible by reason of the provision of the battery 32. Such current flow through 3| causes signals to be applied to grid 28 and the consequent impulses set up across resistance 33 control the frequency of the time base circuit.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:

1. A cathode ray device comprising an envelope, means within the envelope to develop a beam of electrons, a parallel plate condenser within the envelope, means to direct the beam of electrons between the plates of said condenser means to charge the condenser, and means to discharge the condenser through thedeveloped beam,

2. In a cathode ray system, means for developing a beam of electrons, means for moving said beam along a predetermined path, and a serially connected resistor and voltage source connected directly to said second named means and cooper-' ating with the developed beam of electrons for cyclically moving's'aid beam over the predetermined path. j

3. A cathode ray device comprising an envelope, means within theenvelope to develop a beam of electrons, a parallel plate condenser within the envelope, means to charge the condenser, means to direct the beam between the plates of the condenser, and means to dischargethe condenser.

, through the developed beam.

within the envelope, means to direct the beam of' electrons between the plates of said condenser, a

serially connected battery and resistor for charging the condenser, and means to discharge the condenser through the developed beam.

6. A saw-tooth wave generator comprising an envelope, means within the envelope'to generate a beam of electrons, a parallel plate condenser within the envelope, a serially connected battery and resistor for charging the condenser, an auxiliary electrode withinth'e envelope, and means to discharge the condenser through the developed beam and the auxiliary electrode.

7. A cathode ray device comprising an'envelope, r

a right angle plate mounted within said envelope, a second plate parallel to one face of the right angle plate mounted'within the envelope, means within the envelope for'developing a beam of electrons, meansto electrically charge the twoplates, means to direct they developed beam of electrons between the two plates whereby the beam is; deflected toward the right angle plate in accordance with the electrical charging'of the plates; and

means to discharge the plates through the:de-

veloped beam whenever the developed beam impinges upon the right angle plate. H t A 8. In a cathode ray ,tube wherein is provided means for generating a beam of electrons together with a pair of deflecting plates, the method of generating a saw-tooth deflecting potential which comprises the steps of. providing a'source of po I tential, charging the pair of deflecting platesfrom the source of potential, and dischargingthe charge through the generated beam of electrons,

9. Acathode ray device, comprising means for developing a beam, a pair of electrodes, seriallyconnected resistance and condenser connected;

between said electrodes, electrical supply means. 'for passing current through said resistance to,

charge said condenserand means for discharging said condenser through the developed beam.

10. A cathode ray device, comprising means for a developing a beam, a pair of electrodes, serially connected resistance and condenser connected between said. electrodes, electrical supply means v for passing current through said resistance to charge said condenser, an auxiliary electrode'com V nected to one terminal of said condenserfand means for discharging said condenser throughthe developed beam and auxiliary electrode.

' LEONARD "MORRIS ROBERT CADZOW. 

